302 Targeted Inhibition of the Epigenetically Activated miR-483-5p IGF-2 Pathway as a Novel Therapeutic Strategy for Meningioma

INTRODUCTION: Meningioma is the most common primary central nervous system tumor. These are usually treated by surgical resection with curative intent, however gross total resection is not always feasible and there are many cases of recurrent and refractory disease despite adjuvant radiotherapy. Presently, there is no effective pharmacotherapeutic options for these tumors. METHODS: Small RNA sequencing was performed on meningioma tumor samples to study grade-dependent changes in microRNA expression. Gene expression was analyzed by chromatin marks, qRT-PCR and western blot. miRNA modulation, anti-IGF-2 neutralizing antibodies, and inhibitors against IGF1R were evaluated in a tumor-derived primary cultures of meningioma cells. RESULTS: Meningioma tumor samples showed high, grade-dependent expression of miR-483-5p, associated with high mRNA and protein expression of its host gene IGF-2. Inhibition of miR-483-5p reduced the growth of cultured meningioma cells, whereas a miR-483 mimic increased cell proliferation. Similarly, inhibition of this pathway with anti-IGF-2 neutralizing antibodies reduced meningioma cell proliferation. Small molecule tyrosine kinase inhibitor blockade of the IGF-2 receptor (IGF1R) resulted in rapid loss of viability of cultured meningioma tumor-derived cells, suggesting that autocrine IGF-2 feedback is obligatory for meningioma tumor cell survival and growth. The observed IGF1R-inhibitory IC50 for GSK1838705A and Ceritinib in cell-based assays along with the available pharmacokinetics data predicted that effective drug concentration could be achieved in vivo as a new medical treatment of meningioma. CONCLUSIONS: Meningioma cell growth is critically dependent on autocrine miR-483/IGF-2 stimulation and the IGF-2 pathway provides a new feasible meningioma treatment target.